"""Command completion helpers for VimEditor."""
from __future__ import annotations

from pathlib import Path

from vimkit.commands import COMMANDS


def list_path_matches(cwd: Path, partial: str) -> list[str]:
    try:
        if "/" in partial:
            dir_part, name_part = partial.rsplit("/", 1)
            base = (cwd / dir_part).expanduser().resolve()
            prefix = dir_part + "/"
            lower = name_part.lower()
        else:
            base = cwd
            prefix = ""
            lower = partial.lower()
        if not base.is_dir():
            return []
        return sorted(
            prefix + path.name + ("/" if path.is_dir() else "")
            for path in base.iterdir()
            if lower in path.name.lower()
        )[:20]
    except Exception:
        return []


def compute_command_completions(cmd_buf: str, cwd: Path, commands: dict[str, str] | None = None) -> list[str]:
    commands = commands or COMMANDS
    stripped = cmd_buf.lstrip()
    if not stripped or " " not in stripped:
        lower = stripped.lower()
        return [
            cmd + (" " if cmd in ("e", "w", "wq", "cd") else "")
            for cmd in commands
            if lower in cmd.lower()
        ]

    if stripped.startswith("e ") or stripped.startswith("w ") or stripped.startswith("wq "):
        partial = cmd_buf[2:]
        if stripped.startswith("wq "):
            partial = cmd_buf[3:]
        return list_path_matches(cwd, partial)

    if stripped.startswith("cd "):
        partial = cmd_buf[3:]
        named = [name for name in ("projects", "notebooks") if partial == "" or name.startswith(partial.lower())]
        file_matches = list_path_matches(cwd, partial) if partial else []
        return named + [match for match in file_matches if match not in named]

    return []


def apply_completion_text(cmd_buf: str, completions: list[str], index: int) -> str:
    if not completions:
        return cmd_buf
    stripped = cmd_buf.lstrip()
    selected = completions[index % len(completions)]
    if " " not in stripped:
        return selected
    for prefix in ("e ", "w ", "wq ", "cd "):
        if stripped.startswith(prefix):
            return prefix + selected
    return cmd_buf